A stent is commonly used as a tubular structure left inside the lumen of a duct to relieve an obstruction. Commonly, stents are inserted into the lumen in a non-expanded form and are then expanded autonomously (or with the aid of a second device) in situ. When used in coronary artery procedures such as an angioplasty procedure for relieving stenosis, stents are placed percutaneously through the femoral artery. In this type of procedure, stents are delivered on a catheter and are either self-expanding or, in the majority of cases, expanded by a balloon. Self-expanding stents do not need a balloon to be deployed. Rather the stents are constructed using metals with spring-like or superelastic properties (i.e., Nitinol), which inherently exhibit constant radial support. Self-expanding stents are also often used in vessels close to the skin (i.e., carotid arteries) or vessels that can experience a lot of movement (i.e., popliteal artery). Due to a natural elastic recoil, self-expanding stents withstand pressure or shifting and maintain their shape.
As mentioned above, the typical method of expansion for balloon expanded stents occurs through the use of a catheter mounted angioplasty balloon, which is inflated within the stenosed vessel or body passageway, in order to shear and disrupt the obstructions associated with the wall components of the vessel and to obtain an enlarged lumen.
Balloon-expandable stents involve crimping the device onto an angioplasty balloon. The stent takes shape as the balloon is inflated and remains in place when the balloon and delivery system are deflated and removed.
In addition, balloon-expandable stents are available either pre-mounted or unmounted. A pre-mounted system has the stent already crimped on a balloon, while an unmounted system gives the physician the option as to what combination of devices (catheters and stents) to use. Accordingly, for these types of procedures, the stent is first introduced into the blood vessel on a balloon catheter. Then, the balloon is inflated causing the stent to expand and press against the vessel wall. After expanding the stent, the balloon is deflated and withdrawn from the vessel together with the catheter. Once the balloon is withdrawn, the stent stays in place permanently, holding the vessel open and improving the flow of blood.
Additionally, the presence of vessel side branches has had a major influence on the strategy of angioplasty for over a decade. It is common thought that over half of angioplasty procedures may place a vessel side branch in danger. The presence of side branches may also increase procedural complications. The occlusion rate of side branches during coronary angioplasty ranges from 3-15%, depending on the clinical and anatomic features of the vessels. Stents may improve or worsen the flow through vessel side branches in both elective and bailout settings. The concept of “stent jail” is described as the incarceration of vessel side branches when their ostia are covered and made inaccessible by trunk vessel stenting.
To date, there have been no adequate stent designs or methods for stenting a bifurcated vessel that can avoid the problem of stent jailing in any appreciable or reportable way. The present invention is directed toward solving this stent jailing problem through a novel stent and novel method of use.